Solid particle injector

ABSTRACT

AN INJECTOR IN WHICH A SLOW MOVING PLUNGER RECIPROCATES IN A CYLINDER TO INJECT A LIQUID HAVING A HIGH CONCENTRATION OF SOLID PARTICLES SUSPENDED THEREIN INTO A STREAM OF FLUID UNDER A HIGH PRESSURE. THE INLET VALVE OF THE INJECTOR INCLUDES AN INNER, UPWARDLY OPENING VALVE SEAT TAPERING DOWNWARDLY AT 19 TO 23 DEGREES ON WHICH A VALVE BALL SEATS DURING THE PRESSURE STROKE OF THE PLUNGER. THE OPENING AT THE UPPER END OF THE VALVE SEAT HAS A RADIUS SUCH THAT THE SPACE BETWEEN THE SEAT AT ITS UPPER END AND THE BALL IS NOT MORE THAN 0.01 INCH. A DEFORMABLE ANNULAR VALVE SEAL SUPPORTED ON THE UPPER SURFACE OF THE VALVE SEAT SURROUNDING THE TAPERED SURFACE ENGAGES THE VALVE BALL AND HAS A THICKNESS SUCH THAT THE VALVE SEAL EXTENDS ABOVE THE HORIZONTAL CENTERLINE OF THE VALVE BALL WHEN THE BALL RESTS ON THE VALVE SEAT. THIS INVENTION RELATES TO APPARATUS FOR INJECTING SOLID PARTICLES INTO A STREAM OF FLUID UNDER HIGH PRESSURE.

Feb. 9, 1971 w, A L ETAL. I 3,561,822

7 SOLID PARTICLE INJECTOR I Filed April 25, 1968 2 Sheets-Sheet 1 avian/mes; 551 14 GAYLORD ERNEST 4. MOR/ ROBERTJ. 6000M T T JOSEPH L. PEA AREA Feb. 9, 1971 E. w. GAYLQRD ET Al. 3,561,822

' SOLID PARTICLE INJECTOR Filed April 25, 1968 2 Sheets-Sheet 2 //v1 4 ra1 55? 14 cur 4090 ROEEQTJ. 6000M EQ/VESTA. MOR/ JOSEPH L. psmef United States Patent 3,561,822 SOLID PARTICLE INJECTOR Eber W. Gaylord, Pittsburgh, Robert .I. Goodwin, Oakmont, Ernest A. Mori, Hampton Township, Allegheny County, and Joseph L. Pekarek, Penn Hills Township, Allegheny County, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware Filed Apr. 25, 1968, Ser. No. 723,996 Int. Cl. B65g 53/30 US. Cl. 302-14 3 Claims ABSTRACT OF THE DISCLOSURE An injector in which a slow moving plunger reciprocates in a cylinder to inject a liquid having a high concentration of solid particles suspended therein into a stream of fluid under a high pressure. The inlet valve of the injector includes an inner, upwardly opening valve seat tapering downwardly at 19 to 23 degrees on which a valve ball seats during the pressure stroke of the plunger. The opening at the upper end of the valve seat has a radius such that the space between the seat at its upper end and the ball is not more than 0.01 inch. A deformable annular valve seal supported on the upper surface of the valve seat surrounding the tapered surface engages the valve ball and has a thickness such that the valve seal extends above the horizontal centerline of the valve ball when the ball rests on the valve seat.

This invention relates to apparatus for injecting solid particles into a stream of fluid under high pressure.

Several types of processes use suspensions of solid particles in fluids at high pressures. For example, in the hydraulic fracturing process used to stimulate flow from oiland gas-bearing formations into wells, propping agents are suspended in a liquid which is pumped down the well and into a fracture in an underground formation. The pressure on the liquid must exceed the pressure caused by the weight of the formation above the fracture to hold the fracture faces apart and permit entry of the propping agent into the fracture.

A more recently developed process is the hydraulic jet drilling process in which the borehole of a well is drilled by discharging streams of an abrasive-laden liquid at extremely high velocities against the bottom of the borehole to cut into the bottom of the borehole. Slurries ordinarily having a concentration of about 2-6 percent by volume abrasive are usually used in the jet drilling process. Pressure drops of the order of 5000 psi. through nozzles in the jet bit used in the hydraulic jet drilling process are required to impart the high velocity necessary for acceptable drilling rates.

The slurry or suspension of solid particles in a liquid at a high pressure is ordinarily obtained in both the hydraulic fracturing and hydraulic jet drilling process by first suspending the particles in a liquid and then passing the suspension through a pump to raise the pressure to the desired level. That technique heretofor has not been wholly satisfactory for raising the pressure on abrasiveladen liquids to the level desired for hydraulic fracturing and hydraulic jet drilling operations. In hydraulic fracturing the maximum size of the propping agent particles is determined largely by the maximum size that will pass through the valves of the pump. Thus, the pump rather than the optimum conditions for fracturing determines the size of propping agent used.

Pumps used to supply the high-pressure liquid used in processes such as hydraulic fracturing or hydraulic jet drilling must have a high volumetric capacity to supply 3,561,822 Patented Feb. 9, 1971 ice the necessary volume of liquid. The pumps capacity is obtained by operating the pumps at high speed. Solid particles suspended in liquid that passes through pumps designed for a high-pressure operation seriously interfere with the operation of the pumps. The solid particles become lodged under the rapidly acting valves and prevent closing of the valves. Part of the liquid then leaks through the valves and the volumetric capacity, as well as the maximum pressure produced by the pump, is seriously reduced. Usually the solid particles will be of an abrasive nature which causes rapid wear of the valves. Valves leaking because of wear also reduce the volumetric capacity and the pressure produced by the pumps.

One method that has been used to inject solid particles into a high-pressure stream involves the use of a pair of transfer cases. Solid particles are placed in one transfer case, and the pressure on that case is then increased by pumping a clean liquid into the case. The particles are then discharged at the desired rate from the case into the high-pressure stream of liquid. While the particles are being discharged from one transfer case, the other transfer case is being filled. The intermittent operation of the transfer cases demands careful control which results in high labor costs.

This invention resides in apparatus for injecting solid particles into a fluid stream under high pressure. A plunger slowly reciprocates in a cylinder to draw a suspension having a high concentration of solid particles from a lowpressure source into the cylinder and discharge the particles from the cylinder into the high-pressure stream. Freely acting check valves are connected at the inlet and outlet of the cylinder. The valves have a valve seat with an upwardly opening seating surface tapered at a slight angle in the range of 19 to 23 on which a ball rests when the valve is in a closed position. A deformable valve seal of rectangular cross section having an inner opening with a diameter at least as large as the diameter of the upper end of the seating surface is positioned on the upper surface of the valve seat. Upward movement of the ball is limited by a ball guide and ball retainer.

In the drawings:

FIG. 1 is a fragmentary side view, partially in vertical section, of apparatus constructed in accordance with this invention for the injection of abrasive particles into a high-pressure stream;

FIG. 2 is a vertical sectional view through one of the check valves located at the inlet and outlet of the injector illustrated in FIG. 1; and

FIG. 3 is a horizontal sectional view taken along section line IIIIII in FIG. 2.

Referring to FIG. 1, an injector 10 useful in hydraulic jet drilling operations, for example, for injecting solid particles into a high-pressure stream of drilling liquid is illustrated mounted on a suitable frame 12 which is supported on skids 14 to facilitate installation at a drilling rig. The injector 10 includes an injector cylinder 16 in which a plunger 18 reciprocates slowly from a withdrawn position illustrated in FIG. 1 to a forward position at which the end 20 of the plunger 18 is spaced slightly from the head end 22 of cylinder 16 as indicated by broken line 23. The end of the plunger 18 opposite end 20 is connected to a piston 24 driven by a conventional hydraulic cylinder 26. Connection of piston 24 to the plunger 18 is made by an adapter 28 and clamp ring 30. Clamp ring 30 overlaps a shoulder 32 on the end of plunger 18 and is held in place on adapter 28 by suitable cap screws, not shown in FIG. 1.

Plunger 18 is supported midway between the hydraulic cylinder 26 and injection cylinder 16 by a bearing 34 mounted in a pillow block 36. A packing gland 38 in the power end of cylinder 16 nearest the hydraulic cylinder 26 engages the plunger to prevent leakage from the injector cylinder 16.

At the head end 22 of the injector cylinder 16 are an inlet 40 and an outlet 42. Connected to the inlet 40 is an inlet check valve 44 which is connected at its lower end to a supply line 46 for delivery of an abrasive-laden liquid to the injector. An outlet check valve 48 is connected to outlet 42. The novel inlet check valve 44 is highly advantageous in handling highly concentrated suspensions of solid particles in a liquid, and is particularly advantageous when used with the slowly reciprocating plunger 18 in cylinder 16. Outlet valve 48 is preferably of the same construction as valve 44. The upper end of the outlet valve 48 is connected to a line 50 containing the fluid under high pressure into which the abrasive particles are to be injected.

FIG. 1 illustrates only one-half the preferred arrangement in which the hydraulic cylinder is double acting to drive a piston which in turn drives a plunger in an injector cylinder corresponding to cylinder 16 at the end of the hydraulic cylinder opposite cylinder 16. Thus, the end of the injector apparatus not shown in FIG. 1 is substantially a mirror image of the apparatus shown in that figure timed 180 out of phase with plunger 18.

As shown in FIG. 2, valve 44 comprises a valve body made up of a valve seat housing 52 and a retainer housing 54 suitably secured together by means such as bolts 55. An O-ring 56 prevents leakage between the lower surface of retainer housing 54 and the upper surface of seat housing 52.

A central opening 53 extends upwardly through the seat housing 52 and retainer housing 54. An annular shoulder 58 around the central opening in the seat housing supports a valve seat 60 having an inner, upwardly facing seating surface 61. The central opening 53 is enlarged above the valve seat 60 to form a second shoulder 62. A deformable valve seal 64 is supported on shoulder 62 and the upper end of valve seat 60. A sleeve-like valve guide 66 resting on valve seal 64 has a plurality of knife edges 68, best shown in FIG. 3, extending inwardly therefrom to provide guidance for a valve ball 70, preferably made of a tungsten carbide alloy, adapted to seat on seating surface 61 of valve seat 60. The inner diameter of the sleeve-like portion of valve guide 66 is larger than the diameter of the opening in valve seal 64 to leave the upper inner edge of the valve seal unconfined. A cylindrical valve retainer 72 within the retainer housing 54 rests on the upper surface of seat housing 52 and the upper end of the valve guide 66. Fingers 74 extend inwardly from the outer sleeve on the ball retainer to engage the ball 70 and limit its upward movement.

The highly abrasive nature of a suspension of solid particles in a liquid, whether the solid particles are steel abrasives such as are used in hydraulic jet drilling or catalyst particles useful, for example, in catalytic cracking, subjects the check valve to severe wear. The principal wear is of the valve seal 64. Wear of the seating surface of the valve seat is not a serious problem as long as the final seal preventing flow through the closed valve is by the valve seal.

We have found that the life of the valve seal 64 can be greatly extended if the valve seal and the valve seat fit within certain limitations. It is important to minimize extrusion of the valve seal into narrow spaces between metallic surfaces where the resultant thin section of the material from which the seal is made is readily cut by solid particles. It is also essential that deformation of the seal be limited. The useful life of the valve seal 64 can be greatly increased if the space between the valve ball and the upper edge of the valve seat when the valve ball is in the closed position does not exceed 0.01 inch. That narrow opening does not provide sufficient space for substantial extrusion of the seal.

To obtain the desired narrow spacing between the upper edge of the seating surface and the ball, the seating surface should taper inwardly at an angle of 19 to 23 from the vertical. More rapid taper will result in a more rapid wear of the valve seal. For example, with a valve seat tapering at 30, the seal wore out in about four hours when handling a ferrous abrasive-laden liquid at 4 cycles per minute. With a valve seat having a seating surface tapering at 23 operating at the same conditions on the same abrasive-laden slurry at 4 cycles per minute, the valve seal was in good condition after 14 hours of operation. Decreasing the taper to 19 results in negligible extrusive wear of the valve seal. If the taper is reduced still further, the rate of wear is not increased but the valve ball tends to become wedged in the seat. If the valve seat has a seating surface curved to fit the curvature of the valve ball, the taper at the upper edge of the seating surface may be less than 19 without difficulty with the valve ball becoming wedged in the seat.

To prevent excessive deformation of the valve seal, the diameter of the upper edge of the seat must be not more than ,4 inch smaller than the diameter of the valve ball. A larger differential in the two diameters provides excessive space between the valve ball and the upper surface of the valve seat into which the valve seal can be deformed when subjected to high pressure.

The valve seal 64 is of rectangular cross section. If an O-ring is mounted in a groove above the valve seat to provide the final seal, the O-ring becomes extruded into the downstream clearance and is rapidly worn. The valve seal is held in place at a position spaced substantially from its upper inner edge to facilitate release of the valve ball when the pressure within the retainer housing -54 is reduced.

The diameter of the opening in valve seal 64 should be at least as large as the diameter of the upper opening of the seating surface of the valve seat to avoid the valve seal hanging over the edge of the upper seating surface. The diameter of the opening in the valve seal may range from inch smaller to inch larger than the diameter of the valve ball. Only slight deformation of the valve seal is required on the application of pressure to give a tight seal when the diameter of the valve seal exceeds the diameter of the valve ball by V inch or less. The valve seal is constructed of a deformable, relatively hard material such as rubber or neoprene having a Shore durometer hardness in the range of 40 to 70. It is important that the seal have a thickness such that the seal extends upwardly beyond the horizontal center line of the valve ball when the valve ball is resting on the seating surface 61. A thickness of /2 inch is in practically all instances adequate and provides a valve seal that can be deformed enough to prevent leakage through the valve without producing appreciable stresses in the seal.

In the operation of the injector illustrated in FIG. 1 of the drawings, the plunger 18 is reciprocated at a slow rate such as 4 to 10 cycles per minute from the position illustrated in FIG. 1 to a forward position indicated by broken line 23. A suspension of abrasive particles in a liquid is supplied through line 46 and inlet valve 44 to the injector cylinder 16. The supension will contain a high concentration, such as 50-70 percent by volume, of abrasive particles. The ability of the injector of this invention to handle a suspension containing a very high concentration of solid particles enables the injector to discharge a large volume of particles into high pressure line 50 even though the injector operates at a low speed of 4 to 10 cycles per minute.

Assuming that the cylinder 16 is filled with the suspension of abrasive particles, movement of plunger 18 to the left until the end 20 reaches the position indicated by broken line 23 causes an increase in the pressure above the ball 70 to valve 44. Ball 70 is forced downwardly through the opening in valve seal 64 until it engages seat 60. When the diameter of the opening in the valve seal is larger than the diameter of the valve ball, the high pressure within the valve 44 above the seal 64 deforms the valve seal inwardly against the ball 70 to provide an effective seal preventing fiow downwardly through the valve. Meanwhile the high pressure within the cylinder '16 raises the ball in outlet valve 48 off the seat in that valve to allow flow through valve 48 into line 50.

When the plunger 18 moves to the right, the pressure within the valve 44 above the ball is reduced and the valve seal 64 returns to its original condition. Ball 70 moves freely off the seat 60 to allow flow of the abrasiveladen liquid into the cylinder. The knife edges 68 of valve guide 66 oifer no opportunity for solid particles to become trapped between the guide and ball 70 to interfere with movement of the ball 70. The low speed at which the plunger 18 is reciprocated gives the ball valve of this invention adequate time to move onto or off the seat as required to eliminate the necessity of a mechanically driven valve mechanism. The long stroke and slow speed of the plunger also reduces the number of times the valve closes for injection of a given amount of solids, and thereby reduces wear of the valve seal.

This injector is highly advantageous for injecting solid particles into high-pressure streams of gas or liquid, for example, streams at pressures in the range of 500 to 15,000 p.s.i., where screw feeders, standpipes and other types of feeders are not suitable, The disadvantages of multiple transfer cases for delivering particles into highpressure streams are eliminated in this invention.

The injector of this invention has been described for use in hydraulic jet drilling but is not limited to that use. It is suitable for a wide variety of other uses such as the injection of solid particles of catalyst into streams of reactants, or the injection of oil shale particles into fluid streams for release of shale oil and conversion of the shale oil to more valuable products.

We claim:

1. Apparatus for injecting solid particles into a fluid stream at high pressure comprising an injector cylinder having a closed head end and a power end, a plunger slidable in the cylinder, driving means extending through the power end of the cylinder to reciprocate the plunger from a forward position adjacent the head end to a Withdrawn position remote from the head end, an inlet and an outlet opening through the wall of the cylinder adjacent the head end, an inlet check valve connected to the inlet of the injector cylinder and an outlet check valve connected to the outlet of the injector cylinder, said inlet check valve and outlet check .valve comprising a valve body having an opening extending therethrough from a valve entrance to a valve exit, a valve seat surrounding the opening and having a tapered seating surface expanding in the direction of the valve exit, an annular deformable valve seal of rectangular cross section at the exit end of the valve seat, means engaging the exit surface of the seal to hold the seal in place at the exit end of the valve seat, and a ball movable within the central opening from a closed position on the seating surface to an open position spaced from the seating surface; the diameter of the opening in the valve seal is in the range from inch smaller to inch larger than the diameter of the ball, the diameter of the exit end of the valve seat is not more than inch less than the diameter of the ball and the width of the space between the exit end of the valve seat and the ball when at rest on the seating surface is in the range of 0 to 0.01 inch, the diameter of the opening in the valve seal is at least as large as the diameter of the opening in the valve seat at the exit end of the tapered seating surface, and the seal extends toward the valve exit beyond the center line of the ball transverse to the opening when the ball is at rest on the seating surface.

2. Apparatus as set forth in claim 1 in which the driving means are adapted to reciprocate the plunger at about 4 to 10 cycles per minute.

3. Apparatus as set forth in claim 1 in which the seating surface is at an angle to the longitudinal axis of the valve body of approximately 19 to 23.

References Cited UNITED STATES PATENTS 1,170,177 2/1916 Neiswanger l03153 3,009,476 11/1961 Usab l37--516.29 3,400,983 9/1968 Wessel 302-44 ANDRES H. NIELSEN, Primary Examiner US. Cl. X.R. 137516.29 

